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Saturday, January 18, 2014

Artist's rendering of the common ancestor of placental mammals. | Carl Buell

Did the first mammal with a placenta live alongside the dinosaurs — or did it emerge after a gigantic asteroid wiped them out? This is the subject of a heated debate that pits scientists who contend that fossils are the ultimate timekeeper of life’s history against researchers who say that genetics offers more reliable dates.

For that study, Maureen O’Leary, an evolutionary biologist at Stony Brook University in New York, and her team spent several years characterizing and analyzing thousands of traits in dozens of living and fossil mammals. The team combined those characteristics with genetic data to build a giant tree of life, showing how different placental mammals related to one another.

But to establish when the different creatures evolved, the researchers looked only at the fossil record. They concluded that the earliest placental mammals appeared only after the asteroid impact that killed the dinosaurs and marked the end of the Cretaceous period and the beginning of the Palaeogene. After this, the team said, the placentals quickly diversified, and a menagerie of mammals filled the habitat niches left by the dinosaurs.

Phil Donoghue, a palaeobiologist at the University of Bristol, UK, and his collaborators were not convinced. O'Leary's work was “an incredibly impressive study in all aspects — except the timescale in evolutionary history”, he says. “What we were really concerned about is that this stuff was going to end up in textbooks.”

Fossil boundary

Now, Donoghue and evolutionary geneticists Mario dos Reis and Ziheng Yang of University College London publish a study in Biology Letters, saying that O’Leary’s team made a fatal error in assuming that lineages of species date back no further than their oldest fossils. The fossils should instead mark the minimum age for a lineage, says Donoghue, because it is likely that animals existed before that, but were not preserved as fossils or their remains have yet to be discovered.

Using a mathematical elaboration of this concept and genome data from dozens of mammals, Donoghue’s team calculated new dates for the placental-mammal family tree. The researchers conclude that placental mammals first emerged between 108 million and 72 million years ago — well before the (non-avian) dinosaurs disappeared.

The critique follows an August 2013 technical comment on O'Leary's paper, in which an independent group also took umbrage with the suggested Palaeogene origin, because, they said, it requires a dramatic increase in the rate of evolution to explain the early diversity of placental mammals.

Hard evidence

O’Leary says that her team wanted to avoid introducing a bias by assuming that placental mammals are older than suggested by the fossil evidence. But Anne Yoder, an evolutionary geneticist at Duke University in Durham, North Carolina, prefers Donoghue, dos Reis and Yang's approach. “It’s hard to say who’s right and who’s wrong, but the weight of the data support the dos Reis conclusion,” she says.

Yoder adds that discoveries have the potential to harmonize molecular and fossil dates. A decade ago she concluded, using genetic data, that the common ancestor of bush babies and lorises lived around 40 million years ago, even though the oldest fossil was less than 20 million years old. While her paper was in press, a team reported a more than 40-million-year-old fossil that matched her predictions.

As for the current debate, “early placental mammals found in the Cretaceous will settle this once and for all”, says Yoder. O’Leary agrees that the question will be decided by fossil evidence, not mathematical models. “I don’t see this as a problem that’s going to be solved by a computer,” she says.This story originally appeared in Nature News.

One of the strangest objects in the solar system may get its first closeup in the coming years.
A team of scientists is mapping out a mission to the huge metallic asteroid Psyche, which is thought to be the exposed iron core of a battered and stripped protoplanet. The proposed mission would reveal insights about planet formation processes and the early days of the solar system, its designers say, and would also afford the first-ever good look at an odd class of celestial objects.

"This is the first metal world humankind will have ever seen," team member Lindy Elkins-Tanton, director of the Carnegie Institution for Science's Department of Terrestrial Magnetism, told SPACE.com last month at the American Geophysical Union's annual fall meeting in San Francisco. "I think this is an opportunity to do some fundamental science that hasn't been done before."

The huge metal asteroid Psyche may have a strong remnant magnetic field.

A protoplanet's core?

The 155-mile-wide (250 kilometers) Psyche, which lies in the main asteroid belt between Mars and Jupiter, consists largely of iron. Scientists think the object is the nearly naked core of a protoplanet whose overlying rock layers were blasted off by massive collisions long ago.

Psyche thus offers a unique opportunity to learn more about the interiors of planets and large moons, whose cores are hidden beneath many miles of rock, Elkins-Tanton said.

"This is absolutely the only core-like object that we know about in the entire solar system," she said.
A robotic mission to Pysche would also help astronomers take the measure of metal worlds, a type of solar system object that scientists know very little about. The project would beam home the first photos and information ever gathered at such a body.

"We know a lot about stony and icy bodies, but what about metal ones?" Elkins-Tanton said. "What does the surface of a metal world look like?"

This simulation shows a "hit-and-run" collision between two large asteroids, the kind of impact that could have stripped the rocky layers from the big metal asteroid Psyche, exposing the protoplanet's iron core.Credit: M. Jutzi and E. Asphaug (U.Bern/ASU)

For example, she added, it's possible that material melted and blasted out by large impacts on Psyche solidifies in a sheet before being lost to space, causing metallic curtains of ejecta to jut from the rims of impact craters.Mission to be proposed in 2015
The researchers' Psyche probe would orbit the huge asteroid for about six months, studying the object's topography, surface features, gravity and magnetic field, among other characteristics, Elkins-Tanton said.

Data gathered by the spacecraft would shed light on how planets began coming together in the first few million years of solar system history, as well as improve scientists' understanding of the interiors of terrestrial planets such as Earth, she added.

The team has been working on the concept for about a year and a half and plans to submit it during the next call for NASA Discovery-class missions, which is expected to come in 2015. Discovery missions are lower-cost efforts capped at $425 million in 2010 dollars, excluding launch-vehicle expenses.

If selected, the Psyche mission could be ready to launch relatively quickly because it requires no new technology development, Elkins-Tanton said. The spacecraft would be based to a large degree on NASA's Dawn probe, which is currently on its way to the dwarf planet Ceres after wrapping up a 14-month campaign at another giant body in the asteroid belt, the protoplanet Vesta.Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com.

Rebecca Morelle reports for Newsnight on the solar lull that is
baffling scientists

"I've been a solar physicist for 30
years, and I've never seen anything quite like this," says Richard Harrison,
head of space physics at the Rutherford Appleton Laboratory in Oxfordshire.

He shows me recent footage captured by spacecraft that have their sights
trained on our star. The Sun is revealed in exquisite detail, but its face is
strangely featureless.

"If you want to go back to see when the Sun was this inactive... you've got
to go back about 100 years," he says.

This solar lull is baffling scientists, because right now the Sun should be
awash with activity.

The Sun's activity may be falling faster than at any
time in 10,000 years

It has reached its solar maximum, the point in its 11-year cycle where
activity is at a peak.

This giant ball of plasma should be peppered with sunspots, exploding with
flares and spewing out huge clouds of charged particles into space in the form
of coronal mass ejections.

The Sun should be at the peak of its activity -
bursting with flares and coronal mass ejections

But apart from the odd event, like some recent solar flares, it has been very
quiet. And this damp squib of a maximum follows a solar minimum - the period
when the Sun's activity troughs - that was longer and lower than scientists
expected.

"It's completely taken me and many other solar scientists by surprise," says
Dr Lucie Green, from University College London's Mullard Space Science
Laboratory.

The drop off in activity is happening surprisingly quickly, and scientists
are now watching closely to see if it will continue to plummet.

"It could mean a very, very inactive star, it would feel like the Sun is
asleep... a very dormant ball of gas at the centre of our Solar System,"
explains Dr Green.

This, though, would certainly not be the first time this has happened.

“Start Quote

It's an unusually rapid decline”

End QuoteProf Mike
LockwoodUniversity of Reading

During the latter half of the 17th Century, the Sun went
through an extremely quiet phase - a period called the Maunder Minimum.

Historical records reveal that sunspots virtually disappeared during this
time.

Dr Green says: "There is a very strong hint that the Sun is acting in the
same way now as it did in the run-up to the Maunder Minimum."

Mike Lockwood, professor of space environment physics, from the University of
Reading, thinks there is a significant chance that the Sun could become
increasingly quiet.

"We estimate that within about 40 years or so there is a 10% to 20% - nearer
20% - probability that we'll be back in Maunder Minimum conditions."

The era of solar inactivity in the 17th Century coincided with a period of
bitterly cold winters in Europe.

Londoners enjoyed frost fairs on the Thames after it froze over, snow cover
across the continent increased, the Baltic Sea iced over - the conditions were
so harsh, some describe it as a mini-Ice Age.

And Prof Lockwood believes that this regional effect could have been in part
driven by the dearth of activity on the Sun, and may happen again if our star
continues to wane.

"It's a very active research topic at the present time, but we do think there
is a mechanism in Europe where we should expect more cold winters when solar
activity is low," he says.

He believes this local effect happens because the amount of ultraviolet light
radiating from the Sun dips when solar activity is low.

This means that less UV radiation hits the stratosphere - the layer of air
that sits high above the Earth. And this in turn feeds into the jet stream - the
fast-flowing air current in the upper atmosphere that can drive the weather.

The results of this are dominantly felt above Europe, says Prof Lockwood.

Cold, snowy winters could become the norm for
Europe

"These are large meanders in the jet stream, and they're called blocking
events because they block off the normal moist, mild winds we get from the
Atlantic, and instead we get cold air being dragged down from the Arctic and
from Russia," he says.

"These are what we call a cold snap... a series of three or four cold snaps
in a row adds up to a cold winter. And that's quite likely what we'll see as
solar activity declines."

So could this regional change in Europe have a knock-on effect on for the
rest of the world's climate? And what are the implications for global
warming?

In a recent report by the UN's
climate panel, scientists concluded that they were 95% certain that humans
were the "dominant cause" of global warming since the 1950s, and if greenhouse
gases continue to rise at their current rate, then the global mean temperature
could rise by as much as 4.8C.

“Start Quote

This feels like a period where it's very strange... but
also it stresses that we don't really understand the star that we live
with”

End QuoteProf Richard HarrisonRutherford Appleton Laboratory

And while some have argued that ebbs and flows in the
Sun's activity are driving the climate - overriding the effect of greenhouse gas
emissions, the Intergovernmental Panel on Climate Change concludes that solar
variation only makes a small contribution to the Earth's climate.

Prof Lockwood says that while UV light varies with solar activity, other
forms of radiation from the Sun that penetrate the troposphere (the lower layer
of air that sits above the Earth) do not change that much.

He explains: "If we take all the science that we know relating to how the Sun
emits heat and light and how that heat and light powers our climate system, and
we look at the climate system globally, the difference that it makes even going
back into Maunder Minimum conditions is very small.

"I've done a
number of studies that show at the very most it might buy you about five
years before you reach a certain global average temperature level. But that's
not to say, on a more regional basis there aren't changes to the patterns of our
weather that we'll have to get used to."

Polar lights - one manifestation of solar activity in
the Earth's magnetosphere - may dim

But this weather would not be the only consequence of a drawn out period of
inactivity, says Dr Green.

"If the Sun were to get very quiet, one of the few things that would happen
is that we'd have very few displays of the northern lights. They are driven by
solar activity, and we'd miss out on this beautiful natural phenomenon," she
explains.

However, there could be positive effects too.

"Solar activity drives a whole range of space weather, and these are
ultimately effects on the electricity networks, on satellites, on radio
communications and GPS on your sat-nav," she explains.

And while scientists cannot discount that the random bursts of activity may
still occur, calmer periods of space weather would help to maintain the
technological infrastructure that we rely so heavily on.

While the full consequences of a quietening Sun are not fully understood, one
thing scientists are certain about is that our star is unpredictable, and
anything could happen next.

"This feels like a period where it's very strange... but also it stresses
that we don't really understand the star that we live with." says Prof
Harrison.

"We have shown the first time, that in particular photosynthesis is possible in micro-niches on the surface of Mars," says Jean-Pierre de Vera, a scientist at the German Aerospace Center's Institute of Planetary Research in Berlin, Germany. On Earth, Antarctic lichen has shown itself capable of going beyond survival and adapting to life in simulated Martian conditions.

The mere feat of surviving temperatures as low as -51 degrees C and enduring a radiation bombardment during a 34-day experiment might seem like an accomplishment by itself. But the lichen, a symbiotic mass of fungi and algae, also proved it could adapt physiologically to living a normal life in such harsh Martian conditions — as long as the lichen lived under "protected" conditions shielded from much of the radiation within "micro-niches" such as cracks in the Martian soil or rocks.
"There were no studies on adaptation to Martian conditions before," said de Vera"Adaptation is very important to be investigated, because it tells you more about the interactions of life in relation to its environment."

Previous Mars simulation experiments focused on simply measuring the survival of organisms at the end of a given time period. By contrast, de Vera and his group of German and U.S. colleagues measured the lichen's activities throughout the experiment that was detailed in the Sept. issue of the journal Planetary and Space Science. They wanted to see whether the lichen had continued its normal activities rather than simply clinging to life in a dormant state.

Two groups of lichen samples were placed inside a Mars simulation chamber about the size of a big pressure cooker, which itself sat within a fridge about the size of an armoire. That allowed researchers to simulate almost everything about Martian conditions such as atmospheric chemistry, pressure, temperatures, humidity and solar radiation — the lone exceptions being Martian gravity and the added contribution of galactic radiation.

Institute of Planetary Research One of the lichen samples in the Mars chamber was exposed to the full brunt of radiation expected on the Martian surface, while the second set of samples received a radiation dose almost 24 times lower to simulate life in the "protected" condition. A third group of lichen samples sat outside the chamber as a control.

Both lichen sample groups survived their month-long period under Martian conditions. But the heavier dose of radiation from a Xenon lamp simulating the surface radiation conditions kept the unprotected sample group from doing much beyond clinging to survival.

Only the "protected" lichen carried on normal activities such as using photosynthesis to turn sunlight into chemical energy for itself. The protected lichen recovered quickly after an initial "shock" period by adapting well enough to steadily ramp up its photosynthetic activities all the way until the end of the experiment.
"We have shown the first time, that in particular photosynthesis is possible in micro-niches on the surface of Mars," de Vera explained.

The lichen chosen for the experiment, called P. chlorophanum, has proven itself a survival champion even before the Mars simulation. Researchers removed lichen samples for testing from its home atop the rocky Black Ridge in Antarctica's North Victoria Land — a frozen, dry landscape not unlike that of many places on Mars.

The latest Mars simulation experiment did not try to simulate the Martian dust storms that can blanket the entire planet for a month. But de Vera points out that lichen can survive in a resting state for thousands of years on Earth while covered with dust, snow or ice.

Lichen don't exist alone as possible Earth survivors on Mars. Other studies conducted by de Vera have suggested that methane-producing bacteria, known as methanogens, could also manage a Martian existence.
"There are important indices that Earth life can survive, to be metabolically active and adapt physiologically to live on Mars during the time periods which have been investigated," de Vera said.
The experiment's results have huge implications for ongoing robotic missions searching for evidence of life on Mars. First, they confirm that such missions would do well to focus on searching for possible Martian life within the "micro-niche" environments beneath the soil or within rocks protected from surface radiation. Second, they lend hope to the idea that Martian life — if at all similar to Earth life — could have indeed survived up until today.

The lichen's remarkable adaptation to Martian conditions suggests a third, equally important lesson — it justifies the ongoing caution of NASA and other space agencies in ensuring that Earth organisms don't accidentally hitchhike a ride to Mars. Such planetary protection measures seem likely to continue until the possible day that humanity decides to colonize Mars and perhaps change the planet's landscape in the process.

Because the surface of Mars today is bone-dry and frozen all year round, it’s difficult to find any place on Earth onside a lab simulation that is truly Mars-like. But two locations, Antarctica’s Upper Dry Valleys and the hyper-arid core of Chile’s Atacama Desert (below), come close. They have become prime destinations for scientists who want to understand the extreme limits of life on Earth and the prospects for life on Mars.

Jocelyne DiRuggiero, an associate professor of biology at Johns Hopkins University in Baltimore, Maryland, studies samples from both locations. She’s interested in the similarities and the differences between the microbial communities that live in these two extreme desert regions. In both places, very little liquid water is present. In the core of the Atacama, years can go by between one rainfall and the next, but it is warm, so when there is precipitation, a significant amount of liquid water is available for a very short time.

In University Valley, one of Antarctica’s Upper Dry Valleys, the availability of liquid water is limited in a different way. University Valley receives more regular precipitation than the Atacama, but it’s so cold there that any precipitation falls in the form of snow and remains frozen.

Antarctica's Dry Valley is an ideal place for scientists to study how the Earth's plumbing was formed; its current landscape was eroded in to existence millions of years ago, and has undergone very little subsequent erosion since. Researchers have labeled the Dry Valleys region a “relic landscape” as it is the only known location on Earth which is the same now as it was millions of years ago.

Johns Hopkins University geologist Bruce Marsh found the Dry Valleys in 1993, what he calls a walk-in “museum” and “the one place on earth where the plumbing system is exposed in this way. You can stand on shelves of solidified lava that were deposited by magmatic activity 180 million years ago,” he said. “It’s awe inspiring.”

“What we do in those environments is try to understand who is there, what those organisms might be doing, how they are distributed,” says DiRuggiero, and whether the organisms are “really active metabolically,” or if instead they’re “just sitting there, because they’ve been brought by the wind.”

DiRuggiero’s primary tool is DNA sequencing. Working with soil samples that weigh one- to two-tenths of a gram each (about a teaspoonful), she extracts the DNA from any microbes present in each sample. She then sends the DNA off to a lab for sequencing.

Sample preparation is a difficult process because there aren’t many microbes in her samples. Each gram of soil contains perhaps one hundred to one thousand, an extremely low number. The same size sample of ordinary soil typically contains ten million to a billion organisms.

Because the microbial populations she’s working with are so small, contamination is a serious problem. She has to be careful not to let skin cells or hair fall into her samples. Sneezing or coughing on them could pollute them. So DiRuggiero does her work under a special hood that prevents contact with outside air. And even then she has problems, because some of the silica filters she uses to extract DNA from her samples arrive from the manufacturer with microbial cells clinging to them.

Although she has had more time to work with samples from the Atacama, DiRuggiero says the University Valley samples are particularly interesting. Because University Valley is both near the South Pole and more than a mile above sea level, the ground there stays frozen even in summer. There are few places in the world where this is true. “It’s about 40 degrees Celsius colder than the Atacama soil,” she says. That’s about 70
degrees Fahrenheit colder.

That temperature difference results in a significant difference in habitability. There are more microbes in University Valley soil than in Atacama soil.

“Right now the only parameter. . .we have measured that differentiates the populations, Antarctica and the Atacama, is the temperature,” DiRuggiero says. In both locations, “the soils are very dry, the soils are very low in organics, they contain a fair amount of salt. The big difference is the temperature. We don’t really know what it means yet.”

It may seem odd that microbes are happier in sub-freezing conditions than in a warm desert. “This is counter to human experience but makes sense for microbes,” Chris McKay, a planetary scientist at NASA Ames Research Center in Moffett Field, California, wrote in an email. “Cold allows them to sleep, which is a good survival mechanism,” he explained, adding that “this result bodes well for life in the cold deserts of Mars.” McKay heads the NASA-funded IceBite team, which is testing a prototype coring drill for possible use on a future Mars mission. The IceBite team obtained the University Valley samples that DiRuggiero studies.

So far DiRuggiero has been working with University Valley samples collected during the IceBite team’s first season in the field, in 2009. She’s looking forward to getting her hands on more-extensive samples collected at the end of 2010, samples that are still making their way back from Antarctica.

Beneath the dry soil layer in University Valley is “what we call ice-cemented ground, which is basically frozen mud. And that mud has been frozen for thousands and thousands of years,” says DiRuggiero. “So the question is, Is there any water available for the micro-organisms, and do we see a difference in the microbial community between the soil above and this ice-cemented ground right underneath?”

There is some evidence, based on climate data collected last year by the IceBite team, that at the interface between the dry soil and the frozen mud, “there might be some melting in the summer,” says DiRuggiero. “There might be water available at least part of the time” and microbes might be “actively growing and metabolizing at least during a small portion of the year.”

“Melting,” in this case, doesn’t mean the soil gets soggy or muddy, or that the temperature gets above freezing. Rather, it means that thin layers of liquid water can form between the sand grains that make up the soil and the ice below it. But that’s plenty of water for microbes. They’re small. They don’t need a lot of water.

“At temperatures above -20ºC (-4ºF) there is a layer of unfrozen water between the sand grains and the ice. These layers can support microbial life at least [down] to -15ºC (5ºF),” McKay explained.
“On Mars today the temperatures of the ground ice are much too cold for this effect to be useful,” he wrote. But Mars wobbles. At present Mars is tilted on its axis at about the same angle as Earth’s.
Five million years ago, however, Mars leaned over at an angle of about 45º, and for nearly half of each martian year (equivalent to about one Earth year), the polar regions received constant sunlight. Back then “the ground ice at the polar regions,” like the site where NASA’s Phoenix spacecraft landed in 2008, “would have been much warmer. We think it would have been in the range of -15ºC to -20ºC. So liquid water layers” in the past were “a possibility.”

The question then is this: If life ever took hold on Mars, back when the planet was warmer and wetter, did a few hardy microbes evolve a survival strategy that let them go into a deep sleep, and then every 10 or 20 million years, when the ground warmed up to -20ºC or so, wake up and put on a little growth spurt?

The answer will have to wait until a follow-up mission to the martian polar regions can dig deeper than Phoenix did. It is just such deep polar drilling that McKay’s IceBite project is working to make possible.

The best example of this I know is global warming, and it's relationship to carbon dioxide and other "greenhouse" gasses. The overall facts are not disputed by scientists and anyone who has studied the issue. Global temperatures have been rising for the last 120-130 years or so, and carbon dioxide has been steadily rising during the same period. Now, correlation doesn't prove cause and effect, so is it just coincidence? That carbon dioxide is a well known greenhouse gas suggests at least some cause -- this is the basic position of the "97% consensus", though I don't know if it has been proven or is just an informed hypothesis. It is certainly reasonable.

Here is a chart that supports this conclusion:

The thick black line was added by me. Why not just do a linear correlation and fit a straight line through the points? One could fit a very nice line, with a correlation coefficient well above 0.9; but this fit is clearly better. The situation with carbon dioxide concentrations is even better:

One could fit an even much better line through this data set; the yearly average line virtually is straight! More, there are serious reasons to assume, if nothing drastic is not done, it will even start to become exponentially increasing in the near future.

Put the evidence of the two graphs together naively and the conclusion is stark: over the rest of the 21st and into the 22nd centuries the globe is going to keep getting warming, even warming exponentially, until at some point the results will be calamitous for human beings and many other species as well. Again, if nothing serious is done, starting now or soon, to abate the situation.

But notice the leveling out or even cooling, starting about 2005. A blip, or the beginning of another cooling episode, like that of 1940-1975. What does it mean? I suggest we simply have insufficient data to tell yet. And there is serious debate, with most climate scientists/organization insisting the world is still warming. But look at this:

Starting around 1980 global temperatures and solar activity begin to diverge. Even solar scientists didn't predict solar cooling and were completely surprised by this. It would, however, explain the cooling (or warming abatement), and if it continues (it is probably part of a cycle) by 2100 we could find ourselves back into Little Ice Age conditions (probably not as cold because of anthropogenic warming). Again, I emphasize that all this -- the warming abatement, the lower solar activity -- didn't come from any computer model -- but plain old observation. Many observations will be made during the century that will be just as unpredicted.

Existing fossils include a relatively small cranium known as Toumaï ("hope of life" in the local Dazaga language of Chad in central Africa), five pieces of jaw, and some teeth, making up a head that has a mixture of derived and primitive features. The braincase, being only 320 cm³ to 380 cm³ in volume, is similar to that of extant chimpanzees and is notably less than the approximate human volume of 1350 cm³.[citation needed]

The teeth, brow ridges, and facial structure differ markedly from those found in Homo sapiens. Cranial features show a flatter face, u-shaped dental arcade, small canines, an anterior foramen magnum, and heavy brow ridges. No postcranial remains have been recovered. The fossil suffered a large amount of distortion during the time of fossilisation and discovery.[citation needed]

Because no postcranial remains (i.e., bones below the skull) have been discovered, it is not known definitively whether Sahelanthropus tchadensis was indeed bipedal or two-footed, although claims for an anteriorly placed foramen magnum suggests that this may have been the case. Some paleontologists[who?] have disputed[why?] this interpretation of the basicranium. Its canine wear is similar to other Miocene apes.[2] Moreover, according to recent information, the femur of a hominid might have been discovered alongside the cranium but never published.[3]

The fossils were discovered in the Djurab Desert of Chad by a team of four led by Michel Brunet; three Chadians, Adoum Mahamat, Djimdoumalbaye Ahounta and Gongdibé Fanoné, and Frenchman, Alain Beauvilain et al.[4][5] All known material of Sahelanthropus were found between July 2001 to March 2002 at three sites (TM 247, TM 266 (which yielded most of the material), and TM 292). The discoverers claimed that S. tchadensis is the oldest known human ancestor after the split of the human line from that of chimpanzees.[6]

Sahelanthropus may represent a common ancestor of humans and chimpanzees; no consensus has been reached yet by the scientific community. The original placement of this species as a human ancestor but not a chimpanzee ancestor would complicate the picture of human phylogeny. In particular, if Toumaï is a direct human ancestor, then its facial features bring into doubt the status of Australopithecus because its thickened brow ridges were reported to be similar to those of some later fossil hominids (notably Homo erectus), whereas this morphology differs from that observed in all australopithecines, most fossil hominids and extant humans.

Another possibility is that Toumaï is related to both humans and chimpanzees, but is the ancestor of neither. Brigitte Senut and Martin Pickford, the discoverers of Orrorin tugenensis, suggested that the features of S. tchadensis are consistent with a female proto-gorilla. Even if this claim is upheld, then the find would lose none of its significance, for at present, precious few chimpanzee or gorilla ancestors have been found anywhere in Africa. Thus if S. tchadensis is an ancestral relative of the chimpanzees (or gorillas), then it represents the first known member of their lineage. Furthermore, S. tchadensis does indicate that the last common ancestor of humans and chimpanzees is unlikely to resemble chimpanzees very much, as had been previously supposed by some paleontologists.[8][9]

A further possibility, highlighted by research published in 2012, is that the human/chimpanzee split is earlier than previously thought, with a possible range of 7 to 13 million years ago (with the more recent end of this range being favoured by most researchers), based on slower than previously thought changes between generations in human DNA. Indeed, some researchers (such as Tim D. White, University of California) consider suggestions that Sahelanthropus is too early to be a human ancestor to have evaporated.[10]

Sedimentisotope analysis of cosmogenic atoms in the fossil yielded an age of about 7 million years.[11] In this case, however, the fossils were found exposed in loose sand; co-discoverer Beauvilain cautions that such sediment can be easily moved by the wind, unlike packed earth.[12]

In fact, Toumaï was probably reburied in the recent past. Taphonomic analysis reveals the likelihood of one, perhaps two, burial(s) which seemingly occurred after the introduction of Islam in the region. Two other hominid fossils (a left femur and a mandible) were in the same “grave” along with various mammal remains. The sediment surrounding the fossils might thus not be the material in which the bones were originally deposited, making it necessary to corroborate the fossil's age by some other means.[13] The fauna found at the site – namely the anthracotheriidLibycosaurus petrochii and the suid Nyanzachoerus syrticus – suggests an age of more than 6 million years, as these species were probably already extinct by that time.

Orrorin

From Wikipedia, the free encyclopedia

Orrorin tugenensis is a postulated early species of Homininae, estimated at .1 to 5.7 million years (Ma) and discovered in 2000. It is not confirmed how Orrorin is related to modern humans. Its discovery was an argument against the hypothesis that australopithecines are human ancestors, as much as it still remains the most prevalent hypothesis of human evolution as of 2012.[1]

The name of genus Orrorin (plural Orroriek) means "original man" in Tugen,[2][3] and the name of the only classified species, O. tugenensis, derives from Tugen Hills in Kenya, where the first fossil was found in 2000.[3] As of 2007, 20 fossils of the species have been found.[4]
The 20 specimens found as of 2007 include: the posterior part of a mandible in two pieces; a symphysis and several isolated teeth; three fragments of femora; a partial humerus; a proximal phalanx; and a distal thumb phalanx. [4]Orrorin had small teeth relative to its body size. Its dentition differs from that found in Australopithecus' in that its cheek teeth are smaller and less elongated mesiodistally and from Ardipithecus in that its enamel is thicker. The dentition differs from both these species in the presence of mesial groove on the upper canines. The canines are ape-like but reduced, like those found in Miocene apes and female chimpanzees. Orrorin had small post-canines and was microdont like modern humans, whereas robust Australopithecenes were megadont. [4]

In the femur, the head is spherical and rotated anteriorly; the neck is elongated and oval in section and the lesser trochanter protrudes medially. While this suggest that Orrorin was bipedal, the rest of the postcranium indicates it climbed trees. While the proximal phalanx is curved, the distal pollical phalanx is of human proportions and has thus been associated with toolmaking, but should probably be associated with grasping abilities useful for tree-climbing in this context.[4]

After the fossils were found in 2000, they were held at the Kipsaraman village community museum, but the museum was subsequently closed. Since then, according to the Community Museums of Kenya chairman Eustace Kitonga, the fossils are stored at a secret bank vault in Nairobi.[5]
If Orrorin proves to be a direct human ancestor, then australopithecines such as Australopithecus afarensis ("Lucy") may be considered a side branch of the hominid family tree: Orrorin is both earlier, by almost 3 million years, and more similar to modern humans than is A. afarensis. The main similarity is that the Orrorin femur is morphologically closer to that of H. sapiens than is Lucy's; there is, however, some debate over this point. [6]

PUBLISHED: 19:04 EST, 17
January 2014 | UPDATED:
06:47 EST, 18 January 2014 The Sun's activity is at its lowest for 100
years, scientists have warned. They say the conditions are eerily similar to
those before the Maunder Minimum, a time in 1645 when a mini ice age hit,
Freezing London's River Thames. Researcher believe the solar lull could cause
major changes, and say there is a 20% chance it could lead to 'major changes' in
temperatures.

Sunspot numbers are well below their values from 2011, and
strong solar flares have been infrequent, as this image shows - despite Nasa
forecasting major solar storms

THE SOLAR CYCLE

Conventional wisdom holds that solar activity
swings back and forth like a simple pendulum. At one end of the cycle, there is a quiet time
with few sunspots and flares. At the other end, solar max brings high
sunspot numbers and frequent solar storms. It’s a regular rhythm that repeats every 11
years.

Reality is more complicated.

Astronomers have been counting sunspots for
centuries, and they have seen that the solar cycle is not perfectly regular.
'Whatever measure you use, solar peaks are
coming down,' Richard Harrison of the Rutherford Appleton Laboratory in
Oxfordshire told the BBC.

'I've been a solar physicist for 30 years, and
I've never seen anything like this.'

He says the phenomenon could lead to colder
winters similar to those during the Maunder Minimum.

'There were cold winters, almost a mini ice
age. 'You had a period when the River Thames
froze.' Lucie Green of UCL believes that things could
be different this time due to human activity. 'We have 400 years of observations, and it is
in a very similar to phase as it was in the runup to the Maunder
Minimum. 'The world we live in today is very different,
human activity may counteract this - it is difficult to say what the
consequences are.'

Mike Lockwood University of Reading says that
the lower temperatures could affect the global jetstream, causing weather
systems to collapse. 'We estimate within 40 years there a 10-20%
probability we will be back in Maunder Minimum territory,' he
said. Last year Nasa warned 'something unexpected'
is happening on the Sun' This year was supposed to be the year of
'solar maximum,' the peak of the 11-year sunspot cycle. But as this image reveals, solar activity is
relatively low.

THE MAUNDER MINIMUM

The Maunder Minimum (also known as the
prolonged sunspot minimum) is the name used for the period starting in about
1645 and continuing to about 1715 when sunspots became exceedingly rare, as
noted by solar observers of the time.

It caused London's River Thames to freeze
over, and 'frost fairs' became
popular.

The Frozen Thames, 1677 - an oil painting by Abraham
Hondius shows the old London Bridge during the Maunder Minimum

This period of solar inactivity also
corresponds to a climatic period called the "Little Ice Age" when rivers that
are normally ice-free froze and snow fields remained year-round at lower
altitudes.

There is evidence that the Sun has had similar
periods of inactivity in the more distant past, Nasa says. The connection between solar activity and
terrestrial climate is an area of on-going research.

'Sunspot numbers are well below their values
from 2011, and strong solar flares have been infrequent,' the space agency
says.

The image above shows the Earth-facing surface
of the Sun on February 28, 2013, as observed by the Helioseismic and Magnetic
Imager (HMI) on NASA's Solar Dynamics Observatory.

It observed just a few small sunspots on an
otherwise clean face, which is usually riddled with many spots during peak solar
activity. Experts have been baffled by the apparent lack
of activity - with many wondering if NASA simply got it wrong.

However,
Solar physicist Dean Pesnell of NASA’s Goddard Space Flight Center believes he
has a different explanation. 'This is solar maximum,' he says.
'But it looks different from what we expected
because it is double-peaked.' 'The last two solar maxima, around 1989 and
2001, had not one but two peaks.'

Solar activity went up, dipped, then rose
again, performing a mini-cycle that lasted about two years, he said.

Researchers have recently captured massive sunspots on the
solar surface - and believed we should have seen more

The same thing could be happening now, as
sunspot counts jumped in 2011 and dipped in 2012, he believes. Pesnell expects them to rebound in 2013: 'I am
comfortable in saying that another peak will happen in 2013 and possibly last
into 2014.'

He spotted a similarity between Solar Cycle 24
and Solar Cycle 14, which had a double-peak during the first decade of the 20th
century.
If the two cycles are twins, 'it would mean
one peak in late 2013 and another in 2015'.

Scientists are saying that the Sun is in a phase of "solar lull" - meaning
that it has fallen asleep - and it is baffling them.

History suggests that periods of unusual "solar lull" coincide with bitterly
cold winters.

Rebecca Morelle reports for BBC Newsnight on the effect this inactivity could have on our
current climate, and what the implications might be for global
warming.

David Strumfels:

The two graphs above shows the relationship between solar activity and global temperatures from 1550-2000. Clearly, very close. The second graph shows the same relationship 1880-2005. Again, strong agreement until ~1980 when the two part ways. Solar activity and global temperatures are (as common sense dictates) closely aligned; the 1980 parting I suspect is due to CO2 build-up overcoming (temporarily?) this alignment. If solar activity remains low for an extended period of time it should slow warming (as from ~2005-2013) or even reverse it; the 20-25 year delay is expected because warming of the oceans, which release their added heat slowly.

WORLDWIDE PATHOGEN: About one-third of the human population is infected with Mycobacterium tuberculosis (cultures shown above), some 13 million of which are actually sick with TB.CDC/GEORGE KUBICA

In 2009, an international consortium of researchers initiated an efficacy trial for a new tuberculosis (TB) vaccine—the first in more than 80 years. With high hopes, a team led by the South African Tuberculosis Vaccine Initiative inoculated 2,797 infants in the country, half with a vaccine called MVA85A and half with a placebo. They followed the children for up to three years and finally announced the result last February. It was not good news (Lancet, 381:1021-28, 2013).
“It did not work,” says Thomas Evans, president and CEO of Aeras, the Rockville, Maryland-based nonprofit that sponsored the trial. The vaccine did not protect children against the deadly disease.

“The whole field was disappointed,” says Robert Ryall, TB vaccine project leader at Sanofi Pasteur, who was not involved in the trial. “And unfortunately the field did not learn much.” The vaccine developers still do not know why MVA85A didn’t work.

The only vaccine currently available in the fight against TB is Bacille Calmette-Guérin (BCG), a live vaccine first used in 1921 and originally derived from a cow tuberculosis strain. Though the exact mechanism of the vaccine’s protection remains unclear, researchers do know that it doesn’t work well: it reduces the risk of a form of TB that is especially lethal to infants, but it does not reliably protect against TB lung infections, which kill more than a million adults worldwide each year.

With every cough or sneeze of an infected individual, TB bacilli fly through the air, and to date have spread to one-third of the world’s population. In most individuals, Mycobacterium tuberculosis (Mtb) lie dormant, never causing sickness. In others, however, the bacteria cause life-threatening lung infections. Some 13 million people around the world are actively sick with TB, and someone dies of the disease approximately every 20 seconds, according to the World Health Organization (WHO).

“The need for a TB vaccine is enormous,” says David Sherman, a tuberculosis expert at the nonprofit Seattle Biomedical Research Institute. And an inadequate vaccine is not the field’s only problem: the four main drugs currently used to treat tuberculosis are also decades old, take six months to rid the body of the bacilli, and are becoming obsolete due to the spread of multidrug-resistant and extensively drug-resistant TB. Despite the gloomy outlook, many researchers are still plugging away, through pharmaceutical-nonprofit partnerships and redesigned basic research efforts, to achieve a happy ending.

Ancient foe

Tuberculosis has plagued humans for thousands of years. Even ancient Egyptians were ravaged by TB, as evidence from mummies has shown. And over those millennia, Mtb has learned to quietly, carefully live within the human body.

“It’s not just a pathogen; in some ways it’s commensal,” says Evans. “It’s been dealing with the human immune system for a long period of time and knows how to go latent and keep itself transmitted.” Of the roughly 2 billion people infected with Mtb, about 90 percent will never get sick, though they are a vast reservoir of the bacteria, fueling the epidemic. And when illness occurs, unlike many infections that involve an acute sickness as the host’s immune system battles the pathogen, tuberculosis infection resembles a chronic disease. “Everything about the infection is slowed down, frankly, in ways we don’t understand,” says Sherman.E. coli, for example, replicates so quickly—about once every 20 minutes—that one cell can grow into a colony of a million overnight. Mtb, on the other hand, only doubles once every 20 hours, and would take three weeks to grow a colony of similar size. Additionally, the human immune system produces antibodies against most pathogens in roughly 5 to 7 days. Antibody production against Mtb takes three weeks, likely because the bacteria are slow to travel to the lymph nodes where an adaptive immune response commences. “TB is exquisitely adapted to long-term survival in a human host,” says Sherman.

The current TB drug regimen relies on a six-month treatment of four antibiotics, all discovered in the 1950s and ’60s and which primarily inhibit cell-wall and RNA synthesis. (See illustration.) Worldwide, about 3.6 percent of new TB cases and 20 percent of recurring infections are multidrug resistant, according to the WHO.

Mtb is not just a pathogen; in some ways it’s commensal.—­Thomas Evans, Aeras

Unfortunately, there isn’t a deep pipeline of drug candidates to fall back on. It wasn’t until December 2012, some 50 years after the last first-in-class approvals, that the US Food and Drug Administration approved a TB drug with a new mechanism of action. Janssen Therapeutics’ bedaquiline (Sirturo) inhibits an ATP synthase enzyme in the bacterium’s cell membrane to prevent the pathogen from generating energy and replicating. (See illustration.) No other anti-TB drugs are close to approval.

TB drug development has been slow for several reasons. For one, the drugs are difficult and expensive to make, and they are primarily needed in developing countries that can’t afford to pay top dollar for a six-month drug regimen. “Working in TB will not drive profit for pharmaceutical companies,” says Manos Perros, head of AstraZeneca’s Boston-based Infection Innovative Medicines Unit. As a result, most recent TB drug development has involved collaborations between big pharma and government institutions or nonprofit advocacy organizations, as well as academia. These are “partnerships that bring resources and funding that make this kind of work, frankly, possible,” says Perros. “This is a space where competitions between pharma and academia are unfruitful.”

Other pharma companies share that sentiment. In February 2013, Glaxo-SmithKline (GSK) opened up the closely guarded doors of their laboratories to share information with the TB research community about 177 compounds from the company’s pharmaceutical library that appear to inhibit Mtb (ChemMedChem, 8:313-21, 2013). The set of compounds has already been sent to nine groups in the U.K., U.S., Canada, The Netherlands, France, Australia, Argentina, and India, according to GSK spokesperson Melinda Stubbee.

But even with this collaborative attitude, the research community has struggled to develop successful new TB drugs, in part because the bacterium hides latent inside cells such as macrophages, and unpredictably becomes active in different sites in the lung. “TB drug development is extremely challenging because a drug has to kill not only the replicating but the nonreplicating bacteria,” says Feng Wang of the California Institute for Biomedical Research in La Jolla. To tackle this problem, Wang, along with Peter Schultz at Scripps Research Institute, also in La Jolla, and William Jacobs at Albert Einstein College of Medicine in New York, used a novel screening method to test the effect of 70,000 compounds on a biofilm of Mtb that simulates the latent version of the bacterium. One compound popped out of the screen: TCA1 killed both replicating and nonreplicating Mtb (PNAS, 110:E2510-17, 2013). It appeared to attack on two fronts: preventing bacterial cell-wall synthesis and inhibiting a bacterial enzyme involved in cofactor biosynthesis, which is likely what makes it effective against nonreplicating Mtb. (See illustration.) The compound has since proven successful in both acute and chronic animal models of TB, and the team is tweaking the chemistry to try and make it even more potent, says Wang.

Pharmaceutical company AstraZeneca is similarly developing a drug that is active against latent bacteria. AZD5847, a type of antibiotic called an oxazolidinone that is typically used to treat staph infections, is able to reach and kill Mtb lodging inside macrophages. The company is currently testing the drug in a Phase 2 efficacy trial in South Africa involving 75 patients. But developing the compound wasn’t easy, notes Perros. “We’ve been investing for a decade. It really takes a long time.”

Seeking a boost

But even if quick-acting, potent drugs were available, Mtb is so abundant and so well adapted to the human population that the only true path to eradication is not treatment, but prevention. “There’s no endgame without a vaccine,” says Aeras’s Evans. “No matter how much we think we should work on drugs or diagnostics, if we’re not working on vaccines, we’ll never get to our final goal.”

The failure of the MVA85A vaccine trial in South Africa last year was disappointing, but at least a dozen other TB vaccine candidates continue in clinical trials. Most of these reflect one of two general strategies for preventing tuberculosis: improve the existing BCG vaccine or, more commonly, boost its effect with a secondary vaccine. BCG, which is given to infants, primes the immune response early in life, so booster vaccines are usually designed to protect adolescents and adults from later infection. The MVA85A vaccine, for example, was a modified viral vector expressing Mtb antigen 85A designed as a booster to BCG.

Vaccine development, however, is hindered by lack of cellular or molecular markers that directly correlate with immune protection from TB, making it difficult to predict how well a vaccine might protect against TB based on the responses of a handful of individuals. “The only tool we have to make sure a vaccine works is a very large, very expensive field trial,” says Evans. And that high price tag, as in TB drug development, has turned numerous pharmaceutical companies off the pursuit of a TB vaccine.

But with financial and research support from nonprofit partners like Aeras—funded by the Bill & Melinda Gates Foundation, among others—a few companies are still in the game. In collaboration with Aeras, Sanofi Pasteur is developing a BCG booster vaccine that began Phase 1/2a safety trials in South Africa last July. It is a recombinant vaccine made up of two TB proteins fused together and coupled with an adjuvant called IC31, which really “drives the immune response,” says Sanofi’s Ryall. Aeras also has another big-pharma partnership with GSK on a vaccine called M72/AS01e, which has been in Phase 1 and 2 clinical trials since 2004, including an ongoing trial in Taiwan and Estonia. The vaccine combines a GSK recombinant antigen called M72, derived from two tuberculosis-expressed proteins, and a GSK adjuvant called AS01e.

Fresh start

With TB drugs and vaccines still in early clinical phases, some scientists are going back to the basics to see if a better molecular understanding of the bacterium itself could assist these programs. “We need to develop vaccines, and we need to develop products, but as we do, it’s very clear that we need to be learning a lot more about the immunobiology [of TB],” says Evans.

Last July, for example, Sherman and colleagues published the first large-scale map of the bacterium’s regulatory and metabolic networks (Nature, 499:178-83, 2013). The team initially plotted the relationships of 50 Mtb transcription factors, and later, all 200, which control the expression of the rest of the bacterium’s genes. “Our hope is that by looking at it in this different way, we can describe different kinds of drug targets than we have ever done before,” says Sherman.

The team found that Mtb is remarkably well networked, so that if a mutation or drug stymies one gene or protein, others step in as backups, allowing the bacterium to continue functioning normally. But targeting transcription factors that control whole networks could shut down an entire system, backups and all. One such network already looks like a promising drug target—transcription factors controlling a group of proteins in the bacterium’s cell membrane that pump antibiotics and other drugs out of the cell. Mtb has so many such pumps that it is extremely difficult to target multiple pumps for treatment, but genes that activate numerous pumps at the same time are a far more promising drug target.

The idea that scientists will soon develop new, better TB drugs and vaccines “helps get me up in the morning,” says Sherman. It’s going to take more breakthroughs than are on the immediate horizon, he adds, “but if we keep at it, we will get there.”

About Me

My formal training is in chemistry. I also read a great deal of physics and biology. In fact I very much enjoy reading in general, mostly science, but also some fiction and history. I also enjoy computer programming and writing. I like hiking and exploring nature. I also enjoy people; not too much in social settings, but one on one; also, people with interesting or "off-beat" minds draw me to them. I also have some interest in Buddhism.

These days I get a lot more information from the internet, primarily through Wiki. Some television, e. g., documentaries, PBS shows like "Nova" and "Nature".

My favorite science writers are Jacob Bronowski ("The Ascent of Man") and Richard Dawkins (his "The Blind Watchmaker" is right up there up Ascent). I also have a favorite writer on Buddhism, Pema Chodron. Favorite films are "Annie Hall" (by Woody Allen), "The Maltese Falcon", "One Flew Over The Cuckoo's Nest", "As Good As It Gets", "Conspiracy Theory", Monty Python's "Search For The Holy Grail" and "Life of Brian", and a few others which I can't think about at the moment.

I love a number of classical works (Beethoven's "Pastoral", "Afternoon Of A Fawn" and "Clair De Lune" by Debussey , Pachelbel's "Canon" come to mind. My favorite piece is probably Gershwin's "Rhapsody in Blue". But I also enjoy a great deal in modern music, including many jazz pieces, folk songs by people like Dylan, Simon and Garfunkel, a hodgepodge of pieces by Crosby, Stills, and Nash, Niel Young, and practically everything the Beatles wrote.

My life over the last few years has been in some disarray, but I am finally "getting it together.". As I am very much into the sciences and writing, I would like to move more in this direction. I also enjoy teaching. As for my political leanings, most people would probably describe as basically liberal, though not extremely so. My religious leanings are to the absolutely none: I've alluded to my interest in Buddhism, but again this is not any supernatural or scientifically untested aspect of it but in the way it provides a powerful philosophy and set of practical, day to day methods of dealing with myself and the other human beings.